Simulation of Stone Column Ground Improvement (Comparison between Axisymmetric and Plane Strain)

Most of the numerical studies on stone columns are based on the unit cell concept. However, the impact of interactions between adjacent columns and between the columns and the surrounding soil has not been investigated thoroughly. In this study, the finite element software, PLAXIS-2D-V8.2, was used to simulate a stone column as a unit cell and as a plane strain model in order to specify the difference between the performances of each model. The key factors that were investigated included the diameter and c/c spacing of the stone columns, friction angle of the stone column material and undrained cohesion of the soft soil. The emphasis of this parametric study was on the settlement improvement factor and excess pore water pressure, since these are critical to the design of stone columns. The main findings of this study were that in the plane strain model, the settlement improvement factor ranged between 2.2 and 3.2, which means that the settlement was improved more than twice. Meanwhile, in the unit cell concept, the settlement improvement factor did not exceed 1.53. The results of the settlement improvement were compared with the theoretical solutions that are commonly used for studies into the behaviour of stone columns. The unit cell model showed a lower peak value of excess pore water pressure than the plane strain model.